ESP32-LyraT-Mini V1.2: Voip Example Problem

[MicroProz]

Hi @ all,
i tested the voip example with Fritzbox as SIP Server.
The registration and call works fine,
but there is a audio delay from phone to lyrat speaker.
From lyrat mic to phone speaker there is no delay.
How can i fix this delay ?
Also, after start, the first call, the mic from the lyrat is dead.
If i retry the call, the mic is working.
The SIP Server (fritzbox) is working normal. With an other
sip client, there are no delays or problems.

Any suggestions ?

Thanks and best regards,
MicroProz